WP 34S will not turn on

[brettpim]

I would say that I am of medium comfort/skill with electronics. I own the external power supply because I have an old microscope that was missing its power supply, but some years ago I did solder a JTAG interface onto a wifi access-point and rescued it from bad firmware so I might be up for this project.

I did just buy some custom USB boards for the WP34S and used one to make a WP34S from another HP-30b I bought. Would I be able to a USB board to fix the board or does it really require a JTAG?

thanks
brett